I was curious as to how many 24" cables i could link together in order to get my 2 L6 arms furthest away from the electronics? If any at all.
I’m wondering if after a certain distance the cables just can’t supply enough power anymore?
Although there is certainly an upper limit based on the physics involved, suffice it to say that servo cables can be “really, really long” and still provide power and control signals. I recently had a project that ran a remote servo out at the end of about 50 feet of standard 3-conductor non-shielded wire, using nothing more than a wall-wart for power, and I didn’t have any problems.
For a directly-connected servo, the only really critical signals are the pulse and ground lines. As long as the servo shares a common ground with the controlling circuit, and the pulses get there in a reasonable facsimile of their original form, where the servo’s power comes from is fairly unimportant. The pulses can be amplified, boosted, translated, converted, and otherwise manipulated, so long as they show up at the servo’s controller board as a positive-going pulse within the range of timings that it is expecting. Of course, the longer your cables are - especially if they aren’t shielded and/or have lots of connectors along their lengths - the more likely you are to pick up noise and spurious signals, which can be misinterpreted by the servo’s electronics. Since you only specified that you’re trying to get them “furthest away”, I can’t give you anything more specific to your application.
One thing to keep in mind: If you’re just extending the servo cables, that’ll be three conductors per servo, times six axes, times two arms, for a total of 39 conductors, a full two thirds of which are redundant power and ground feeds. In truth, all you would really need for an “individual feed” type of scenario would be 14 conductors - 6 servo pulse lines per arm, plus a power and ground.
A better idea would probably be to mount your servo controller (I’ll assume a single SSC-32 driving both of them) at the arms’ location. Then you need only provide three lines - power, ground, and a serial signal to the controller (four if you want to add return data for the SSC-32’s responses). This can be easily provided by commonly available, and relatively thin-diameter, shielded cable. This is still a wired solution, though. If you’re looking at a very long run, then rather than bothering with all of this cable management stuff, it may just be simpler to use some sort of a wireless solution.
The further you run the wire the thicker it should be.
I’ve operated a servo over ~12’ of cat3 phone wire with no problems.
Awesome ideas! I don’t intend to go super crazy lengths i just wanted to make sure that there was a good distance i can go away from the electronics if it was necessary.
At the moment my plan is to run both arms through the SSC-32 but have the board in another location a bit further away from the arms. The distance of this I’m not sure of yet. But its great to know that i can if need be achieve good distances with the proper wiring! Thanks again!
Servo wire length still poses a Q for me.
My scenerio:
Animatronic puppet show.
Using SSC-32, and several servo’s within 4 ft.
I am going to add a few more servo’s at approx. 20 ft.
Dumb Q, but can I run 2 main wires to 2nd location (+V and Gnd) terminal block, And just 1 pulse wire for each servo.
I if so, can the several pulse wires be flat or twisted, or such low voltage it doesn’t matter?
Will phone wire and connectors that are cheap and are easily acquired work?
Thanks,
Ken
Yes you can run the power and the signals like you described, but I would do my best to rout the wires in a single bundle.
You can also make up a buffer (line driver) for the TTL signal, and get greater distances. The power can be local to the servos, just the signal and ground wires need to go the distance.
Parallel port extenders come to mind as an off-the-shelf solution.
You can even go to differential pairs if need be.
Yet another option would be to make the SSC32 board remote, and use a “long serial” (RS-485) solution to the distance problem.
Alan KM6VV
Probably the easiest thing to do is go to the store and get 25’ of cat3 wire, put a servo on the end, and see how well it works. If improvements are needed, then start with possible cheap and easy improvement items and work yourself into the $$$ solutions as needed.